Do you any materials to support the claim that this was deliberate policy rather then a simple consequence of wartime displacement? What is the scale of deportations from the post-war period compared to the total population present? How many of the Balts moved elsewhere in the USSR for personal reasons rather then because they were deported at gun point? The mobility of population in the Soviet Union was much higher then it was in the old Russian Empire. I'm not arguing, I'm genuinely interested in what you base your opinions on.
Look at the figures from independence onward, in that case. The trend is still visible.
I'm not talking about the movement of people to jobs elsewhere in the USSR, but the arrests & forced deportations that accompanied the Soviet occupation & annexation in 1940-41 & the return of the Red Army in 1944-45, & continued up to the beginning of the 1950s. They're well-documented & only the numbers are disputed.
The first deportations, in 1940, seem to have involved relatively few people. Much greater numbers were deported in June 1941, just before the German invasion (so not triggered by it), & more in 1944-45 & 1949. Deportees were allowed to return after 1958, & many of those who were still alive did. There were still obstacles, though, such as being at the back of queues for housing, especially in 'sensitive' areas such as Narva & Dvinsk/Daugavpils.
The following numbers have been estimated for 1944-55, though as I said, they're disputed, & should be taken as an upper bound.
Estonia 124,000
Latvia 136,000
Lithuania 245,000
Pre-war populations of ethnic Estonians & Latvians & Lithuanians, in thousands were -
Estonians 993 (1934) (Russians 94) 1989: 963 & 475
Latvians 1473 (1935) (Russians 206) 1989: 1388 & 906
Lithuania didn't have an influx of Russians on the scale of the others, so it's not such an issue there, & inconveniently, it also didn't have a census after 1923, & that was for a smaller area than the current state. It didn't include Vilnius, for example.